Final answer:
The early ancestors of fish evolved adaptations such as the development of jaws, multiple paired fins, and the ability to survive in both water and on land, mirrored in the transitional fossil Tiktaalik Roseae.
Step-by-step explanation:
Early ancestors of fish developed various adaptations to enhance their survival and diversify, with fish being the earliest vertebrates. One significant adaption was the evolution of jaws in gnathostomes, which allowed them to expand their feeding options to include active predation and facilitated navigation with the development of multiple paired fins. Another notable evolutionary step was the transition from water to land, mirrored in a fossil 'tetrapod-like fish', known as Tiktaalik Roseae; this creature exhibited intermediate characteristics between fishes and early tetrapods, having both gills and lungs, which gave it the capacity to exist in various environments.
Learn more about Fish Adaptations